Everyone asks why the Tardigradus got their most infamous ability: being able to survive even the worst environements in existence. This all comes from their creator, THE Tardigradus.
THE Tardigradus is a god that was created in a Big Bang. In fact, ITS the Big Bang result itself! This could mean it could be one of the smallest sentient universes to exist of all.
In one moment, it decided to spread its power in all universes, as a way to be an omnipresent protector of all existence, but this plan failed, as its "children" were made extremly weak and dumb to actually do something succesful. The only real thing they got from its progenitor (along with the similar appareance) is their ability to survive the worst environements you can imagine. THE Tardigradus got this ability due to the sheer heat and unstability a Big Bang produces, being able to not only survive the explosion itself, but the harsh conditions that occur seconds after the inicial explosion.
THE Tardigradus is now trying to do experiments with itself so in a future be able to create better and stronger Tardigradus, so its objetive is finally a success.